1. Field of the Invention
The invention relates to an electroluminescent display device, particularly to an electroluminescent display device having color filter layers.
2. Description of the Related Art
An organic electroluminescent (hereafter, referred to as EL) element is a self-emissive element. An organic EL display device using the organic EL elements is receiving an attention as a new display device substituted for a CRT or an LCD.
FIG. 6 is a schematic cross-sectional view showing a pixel of a full-color organic EL display device of the conventional art. A numeral 200 designates a glass substrate, a numeral 201 designates an organic EL element driving TFT (thin film transistor) formed on the glass substrate 200, and a numeral 202 designates a first planarization insulating film. A numeral 203 designates an anode layer made of ITO (indium tin oxide) which is connected with the TFT 201 and extends over the first planarization insulating film 202, and a numeral 204 designates a second planarization insulating film formed so as to cover end portions of the anode layer 203. A numeral 205 designates R (red), G (green), and B (blue) organic EL layers each formed on the anode layer 203, and a numeral 206 designates a cathode layer formed on the organic EL layers 205.
A glass substrate 207 covers the cathode layer 206. The glass substrate 207 and the glass substrate 200 are attached at their edges to enclose the R, G, and B organic EL layers 205 therein. Here, the R, G, and B organic EL layers 205 are respectively formed by selectively performing vapor-deposition of each of R, G, and B organic EL materials by using a metal mask.
On the other hand, as a method of realizing a full-color organic EL display device without the above R, G, and B organic EL layers 205, using color filter layers has been proposed. In this method, a combination of a white organic EL layer and color filter layers has been employed.
The organic EL display device of this type is described in Japanese Patent Application Publication No. Hei 8-321380.
However, when employing the combination of the white organic EL layer and the color filter layers, the color filter layers must be disposed under the organic EL layer and the second planarization insulating film. In this conventional EL device, light from the white organic EL layer leaks from the display panel so that color purity lowers.
Therefore, an object of the invention is to prevent lowering of purity of R, G, and B colors by minimizing white light leakage and color mixture caused by an escape of light to an outside of a color filter layer.